Published May 28, 2015 at 6:00 PM | Updated at 8:19 PM EDT on May 29, 2015

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The Nassau County District Attorney's office has opened an investigation into whether a powerful local state senator improperly billed taxpayers for nearly $20,000 in car expenses, sources close to the probe tell NBC 4 New York's I-Team.

Republican Sen. Carl Marcellino of Syosset, who represents the Fifth Senate District, spent more than $20,000 of his campaign funds on automobile expenses between 2010 and 2013, according to campaign finance records.

Because those expenses were paid for by his campaign, it would be against the law for him to bill taxpayers for the same expense. According to records provided to the I-Team, the state reimbursed Marcellino for $18,500 in auto expenses during the same period.

In a statement, Marcellino's communications director, Kathy Wilson, said he had not been contacted by any law enforcement entity concerning "recent claims by a local television station."

"He is confident that he has followed all laws and appropriate guidelines," the statement said.

Marcellino, first elected to the New York State Senate via special election in 1995, of the senate Investigations Committee, Infrastructure and Capital Investment Committee and was recently appointed head of the Committee on Education.

Marcellino also serves as a member on the senate committees on Rules, Finance, Banks, Consumer Protection, Cultural Affairs and Tourism, Education, Environmental Conservation and Labor.

Sources familiar with the investigation say acting Nassau District Attorney Madeline Singas' investigation is ongoing, and her staff has reached no conclusion of wrongdoing.

Her office declined comment.

Susan Lerner, who heads the good government group Common Cause, said she is not aware of the investigation into Marcellino. But she said car expenses are among many areas of lawmaker spending that should he more closely tracked.

"We have a system where anything goes in Albany," she said. "No oversight. No enforcement whatsoever."

So-called double dipping on automobile expenses was one of the subjects Gov. Cuomo's Moreland Commission was looking at before it disbanded. In it's preliminary report, the Democrat's commission listed 10 unnamed lawmakers it was investigating for possible auto expense propriety. Sources tell the I-Team Marcellino was one of them.

The investigation comes after a string of corruption allegations against state lawmakers. Late last year, state Assembly Speaker Sheldon Silver, a Democrat, was arrested on charges of exchanging political favors for payments. He submitted his resignation as speaker in February to fight the charges, and has pleaded not guilty.